Abstract
In this project, our specific focus will be directed towards understanding the interaction between climate warming and two prominent stressors in freshwater habitats: eutrophication (as nitrate pollution) and low dissolved oxygen (hypoxia). Freshwater habitats often receive excessive inputs of nitrates from urban and agricultural sources, and nitrogen is considered the main limiting nutrient for primary production. Nitrate pollution is closely linked to a second stressor - hypoxia. Because of the nitrate pollution, rapid, uncontrolled growth of algal blooms is often triggered, and the unnatural density of algal blooms causes light reduction for macrophytes during the day and nightly hypoxia when photosynthesis is not occurring. In the past it has been postulated that many small fish deplete the zooplanktonic grazers such as daphnids under warm and eutrophic conditions, inducing the turbid waters with algal blooms. However, climate change does not only induce steady increases in temperature but is also causing more frequent and severe heatwaves. In this project we postulate that these heatwaves will seriously negatively affect performance and survival of the fish, which in turn will affect shifts in the aquatic food web towards more zooplankton and hence potential less severe algal blooms.
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